Method and apparatus for producing tube

ABSTRACT

A method and an apparatus for producing a tube from a strip of synthetic resin and/or unvulcanized rubber incorporating a vulcanizing agent by winding the strip on a former supported by a frame in the manner of a cantilever to shape the strip into a tubular body and heating the tubular body on the former by a heater while sending out the tubular body toward the free end of the former.

This is a continuation, of application Ser. No. 776,033 filed Mar. 9,1977, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a method of and an apparatus forcontinuously producing a tube of indefinite length from synthetic resinand/or unvulcanized rubber incorporating a vulcanizing agent.

With conventional techniques, tubes are produced from synthetic resinand/or unvulcanized rubber incorporating a vulcanizing agent by abatchwise operation including two separate steps; the step of shaping atubular body and the step of placing the tubular body into a vulcanizerand heating the tubular body for vulcanization. Accordingly, theoperation is inefficient and involves difficulty in producing elongatedtubes because the length of the tube to be produced is limited by thedimensions of the vulcanizer. Further when tubes are shaped fromsynthetic resin, the step of helically winding an extruded strip into atubular body has the drawback that the adjacent superposed coils of thestrip are not completely intimately fused and bonded to each other dueto a reduction in temperature. Alternatively, when such strip is woundin layers into a tubular body, the adjacent layers are not always fullyintimately fused and bonded to each other.

This invention has overcome such problems.

SUMMARY OF THE INVENTION

This invention provides a method of producing a tube comprising thecontinuous steps of extruding synthetic resin and/or unvulcanized rubberincorporating a vulcanizing agent into a strip, helically winding thestrip on a former into a tubular body, and heat-treating the tubularbody as retained on the former.

This invention further provides an apparatus for producing such tubecomprising a former supported by a frame in the manner of a cantileverfor helically winding thereon a strip of synthetic resin and/orunvulcanized rubber incorporating a vulcanizing agent to shape the stripinto a tubular body and send out the tubular body toward the free end ofthe former, and heating means for heat-treating the tubular bodyretained on the former.

According to the method and apparatus of this invention, a tubular bodyis shaped on the former and heat-treated thereon at the same time. Whenthe tubular body is made from unvulcanized rubber, therefore, the coilsof the strip forming the tubular body can be fused and bonded togethereffectively and the tubular body can be immediately vulcanized by acontinuous operation. The heat treatment ensures more effective fusionand bonding between the coils of the strip when it is made of syntheticresin, making it possible to continuously produce a tube of improveddurability.

An object of this invention is to provide a method of and an apparatusfor producing a durable tube by continuously heat-treating an elongatedtubular body of unvulcanized rubber and/or synthetic resin.

Another object of this invention is to heat-treat a tubular body frominside as it is retained on a former to thereby achieve improvedvulcanizing effect and ensure effective fusion and bonding between coilsof a strip.

Another object of this invention is to render the helical pitch of feedrollers freely settable so that a strip can be wound into a tubular bodywith an adjustable degree of lapping.

Other objects and advantages of this invention will become apparent fromthe following description.

Embodiments of the invention will be described below in detail withreference to the accompanying drawings showing an embodiment of thepresent apparatus and examples of hoses produced by the present methodand apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view schematically showing an apparatus for producinga reinforced rubber hose;

FIG. 2 is a plan view partly in horizontal section showing a principalpart of FIG. 1;

FIG. 3 is a front view partly in vertical section showing the principalpart of FIG. 1;

FIG. 4 is an enlarged front view in vertical section showing anotherprincipal part;

FIGS. 5 (A) and (B) are side elevations in vertical section showinganother principal part;

FIG. 6 is a front view partly broken away and showing the reinforcedrubber hose;

FIGS. 7 to 9 are front views showing finished hoses of differentstructures respectively, each hose being partly broken away to show themain part;

FIGS. 10 to 14 are enlarged front views in vertical section showingfinished hoses of different structures respectively; and

FIG. 15 is a front view partly broken away and showing a finished hoseof another structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an extruder A for continuously extruding a strip 3 onto aformer B supported in the manner of a cantilever. The strip 3 iscomposed of unvulcanized rubber 1 incorporating a vulcanizing agent anda reinforcement 2 of rigid polyvinyl chloride resin embedded in a thickportion of the rubber 1. Within the extruder A, the unvulcanized rubber1 is maintained at up to about 60° C. and the reinforcement 2 at about130° to 180° C. The strip 3 is maintained at about 100° C. when extrudedfrom a die a into the atmosphere. The unvulcanized rubber 1 used hasgood compatibility with rigid polyvinyl chloride resin. Due to theapplication of heat for the extrusion, the unvulcanized rubber 1, whenextruded into the strip 3, has greater toughness than at the atmospherictemperature and is intimately fused and bonded to the reinforcement 2 atthe interface therebetween.

The former B is so constructed as to helically wind the strip 3 into atubular body 4 with its one edge lapping over the other edge whilesending out the tubular body 4 toward the free end of the former B. Theformer B incorporates heating means C₁ and is provided therearound witha heating chamber 5 housing heating means C₂ utilizing infrared raylamps. The heating chamber 5 is disposed at an intermediate portion ofthe length of the former B. The tubular body 4 sent forward while beingretained in shape by the former B is continuously vulcanized by beingheated to 170° to 220° C. from both inside and outside by the heatingmeans C₁ and C₂. The portion of the former B extending from the heatingchamber 5 toward its free end does not include the heating means C₁ butis provided with a cooling water discharge nozzle 6 close to its outerperiphery. Indicated at 7 is an elongated water bath.

Accordingly, the heated and vulcanized tubular body 4 is cooled with thecooling water from the nozzle 6 and is further cooled to the atmospherictemperature by the water bath 7 while floating and traveling thereon,whereby the reinforcement 2 is hardened. Consequently, a reinforcedrubber hose is obtained which is composed of a rubber layer 1a and ahelical reinforcement 2 embedded in a thick portion of the rubber layeras shown in FIG. 6.

The reinforcement 2 and the unvulcanized rubber 1 may have a suitablesectional shape defined by the orifice of the die a. The forward openend of the tubular body 4 is closed with a suitable cap on leaving thefree end of the former B to prevent the water from flowing into the bodywhile it is floating and traveling on the water bath 7.

The construction of the former B will be described below in detail.

With reference to FIGS. 2 and 4, a metal core 8 having a high thermalconductivity is fixedly inserted at its one end to a sleeve 10 screwedto a frame 9 and is thereby supported in the manner of a cantilever. Aplurality of feed rollers 11, supported by a plurality of retainers 12,are helically arranged around the metal core 8 with a large pitch andare in contact with an imaginary cylindrical face (i.e. the innerperipheral surface of the tubular body 4 to be produced) coaxial withthe tubular body. The rollers 11 are rotatable in position each aboutits own axis.

As seen in FIGS. 5 (A) and (B), the retainers 12 are polygonal and areeach formed, in their peripheral portion, with recesses 13 rotatablyreceiving the feed rollers 11. The retainers 12, arranged from thesupported end of the metal core 8 toward the free end thereof, aresecured to the metal core 8 by bolts 14 with the phase of each retainer12 displaced by a specified angle θ from retainer to retainer, wherebythe helical pitch of the feed rollers 11 is settable as desired.

Each of the feed rollers 11 is operatively connected at its base end toone end of a driven shaft 15 by a coupling 16. The driven shaft 15extends through and is rotatably supported by the frame 9. Each drivenshaft 15 has the other end fixedly carrying a pinion 19 meshing with amain gear 18 secured to a drive shaft 17. The input from a pulley 20rotates the drive shaft 17 in one direction, thereby rotating the feedrollers 11 in the direction reverse to the direction of the helixthereof.

With reference to FIGS. 4 and 5 (A) and (B), the heating means C₁incorporated in the former B comprises a nichrome wire heater 21 coveredwith an electric insulator and inserted into bores formedcircumferentially equidistantly in the metal core 8.

According to the construction described above, the tubular body 4 on theformer B is heated by the two heating means C₁ simultaneously frominside and outside, with the result that the tubular body 4 can beheated and vulcanized efficiently and uniformly in its entirety whilebeing retained in shape against possible collapsing.

Particularly since the inner heating means C₁ is incorporated in themetal core 8 having a high thermal conductivity with the feed rollers 11adapted to contact the inner peripheral surface of the tubular body 4,very high heating efficiency is attainable, consequently assuring highlyefficient vulcanization.

The reinforced rubber hose produced by the above apparatus hasoutstanding resistance to oils and heat because the reinforcement 2 ofrigid polyvinyl chloride resin is embedded in the rubber layer 1a.Moreover, the firm bond formed between the reinforcement 2 and therubber layer 1a uniformly over the entire periphery of the reinforcement2 effectively prevents separation therebetween even when the hose issubjected to repeated bending or deformation, thus assuring thereinforcing effect of the reinforcement 2 over a prolonged period oftime.

Although the former B included in the foregoing embodiment is of suchtype that the helical feed rollers 11 are driven in the same directionto shape the strip 3 into a tubular body 4 while sending out the tubularbody toward the free end, the former B may be of any type, insofar asthe strip 3 can be helically wound into the tubular body 4 while sendingthe body toward the free end. For example, formers B of the followingconstructions are useful:

(a) A former B comprising at least two feed rollers 11 rotatable in thesame direction and inclined in the same direction with respect to theaxis of the tubular body 4 to be produced.

(b) A former B comprising rollers rotatable in the same direction andarranged on the same circumference in parallel to one another, and outerrollers having cam surfaces disposed close to the group of rollers orcams arranged at the base ends of the rollers successively displaced inthe axial direction. A tubular body 4 is formed from a strip helicallywound over the group of rollers and is forced toward the free end by theroller cam surfaces or by the cams.

(c) A former B comprising a plurality of rotatable shafts arrangedaround a tubular rotary shaft or on the same circumference, and a belthelically wound around the group of rotatable shafts, the belt havingopposite ends connected together in the hollow portion of the tubularrotary shaft or in a hollow portion defined by the group of therotatable shafts to provide an endless helical rotatable member. A strip3, when helically wound on the rotatable member, is shaped into atubular body 4 while being sent toward the free end.

(d) A former B comprising a plurality of rotatable shafts arranged onthe same circumference in parallel to one another, and sleeves coveringthe shafts respectively and reciprocally slidable only axially thereof.A strip 3 is helically wound around the group of sleeves into a tubularbody 4. Each of the sleeves comprises two divided semicylindricalsegments such that the segments are slidable toward the free end whenbrought into contact with the inner surface of the tubular body 4, thesgements being also slidable in the reverse direction when brought awayfrom the inner surface of the body 4. The tubular body 4 can be sent outtoward the free end by the movement of the sleeves.

The heating means C₁ may also have any of various constructions suitablefor the particular type of the former B used. For example, the nickromewire heater 21 may be provided on the outer peripheral surface of themetal core 8 included in the foregoing embodiment. Alternatively, themetal core 8 may be formed with an oil passage through which ahigh-temperature oil heated outside the former B is circulated.

Irrespective of the type of the former B or of the heating means C₁used, the outer heating means C₂ can be dispensed with depending on theconstruction, material, etc. of the hose to be produced.

For example, FIG. 7 shows a flexible hose comprising a rubber layer 1aprovided only on the inner side of the hose and an outer resin layer 22as of soft polyvinyl chloride resin. The hose can be produced byextruding from the extruder A a strip composed of a soft resin portionand unvulcanized rubber intimately fused and bonded to the entire lowersurface of the resin portion, helically winding the strip on the formerB into a tubular body and simultaneously heating the tubular body frominside by the heating means C₁ within the former B for continuousvulcanization. This method ensures efficient vulcanization of the rubberlayer 1a while minimizing the adverse influence on the soft resin layer22 due to the heat.

FIG. 8 shows the same hose as shown in FIG. 7 except that areinforcement 2 of rigid polyvinyl chloride resin (or metal wire) isembedded in a soft resin layer 22. A rubber layer 1a is vulcanized frominside by the heating means C₁ in the former B.

FIG. 9 shows a hose comprising a tubular portion in the form of a rubberlayer 1a and a rigid resin reinforcement 2 provided helically around thetubular portion. This hose is produced by continuously extruding fromthe extruder A a strip composed of an unvulcanized rubber portion and areinforcement 2 intimately fused and bonded to the top center part ofthe rubber portion, helically winding the strip on the former B into atubular body with one side edge of the unvulcanized rubber portionoverlapping the other side edge thereof, and heating and vulcanizing thetubular body from inside by the heating means C₁ in the former B.

FIG. 10 shows a heat-insulating hose composed of inner and outer resinlayers 23, 24 and a foamed resin layer 25 having a reinforcement 2embedded therein. The hose is made by helically winding on the former Ba strip for forming the layers 23, 24 and 25 into a tubular body, andheating the tubular body from inside by the heating means C₁ within theformer B to foam the layer 25.

Rubber hoses of various structures can be produced by suitably selectingthe extruder, the shape of the die orifice, the material to be embeddedin rubber, the method of embedding, etc.

FIGS. 11 to 15 show typical examples of such hoses. FIGS. 11 and 12 showrubber hoses produced only from rubber 1a. FIG. 13 shows a rubber hosecomposed of rubber 1a lined with a helical fabric piece 26. FIG. 14shows a rubber hose comprising rubber 1a and a string 27 embedded in athick rubber portion and extending in parallel to the axis of the hose.FIG. 15 shows a rubber hose formed by double-pitch helical winding andincorporating two electric wires 28 and 28' embedded in thick portionsof rubber 1a. Although not shown, a hose of multi-layered structure isproduced by helically winding a plurality of strips with repeatedheating, whereby the adjacent layers can be fused and bonded togetherwith improved results. Further when a hose is formed from a resin striphaving higher heat resistance in its inner layer than in the outer layerthereof, the strip is heat-treated from inside, whereby one edge of thestrip can be fused and bonded to the other edge effectively. As aresult, a hose can be produced from thermosetting resin strip.

What is claimed is:
 1. An apparatus for continuously producing a tube comprising:a former (B) supported by a frame (9) in the manner of a cantilever for helically winding thereon a strip (3) of synthetic resin and unvulcanized rubber incorporating a vulcanizing agent to shape the strip (3) into a tubular body (4) and send the tubular body (4) toward a free end of said former (B), heating means (C1 and C2) for heat-treating the tubular body (4) to 170° C. to 220° C. during movement of said strip toward said free end, characterized in that said heating means (C1 and C2) are disposed at least inside and outside said former (B) extending along its length and constructed to heat the tubular body (4) from inside and outside to a temperature of from about 170° C. to about 220° C. for vulcanization thereof, said heating means comprising a nichrome wire heater (21) incorporated in a metal core (8) of the former (B), the former (B) including a plurality of feed rollers (11) helically arranged and retained by a plurality of retainers (12) secured to the metal core (8) and arranged from a supported end of the metal core toward a free end thereof, said retainers (12) being formed with recesses (13) for retaining said feed rollers (11) and are arranged from the supported end of the metal core (8) toward the free end thereof with the phase of each of the retainers (12) displaced by a specified angle (θ) from retainer to retainer, the retainers being securable to the metal core in the displaced positions, whereby the helical pitch of the feed rollers (11) is freely determinable, and a cooling water nozzle (6) disposed on one side of the heating means (C1) toward which the tubular body (4) is sent out to thereby cool the tubular body (4) immediately after the vulcanization heat treatment.
 2. The invention of claim 1 wherein said retainers are polygonal.
 3. The invention of claim 1 wherein said retainers are polygonal and said recesses are disposed along corners of said polygonal retainers.
 4. The invention of claim 1 wherein said nichrome wire heater has an electric insulator covering the nichrome wire heater and a plurality of nichrome wire heaters being disposed circumferentially equidistantly in and inserted into bores formed in said metal core.
 5. The invention of claim 1 wherein said plurality of feed rollers are adapted to contact an inner peripheral surface of said tubular body whereby sufficiently high heating efficiency is attainable and achieving highly efficient vulcanization.
 6. The invention of claim 1 wherein said plurality of feed rollers are adapted to contact an inner peripheral surface of said tubular body whereby a reinforced rubber hose is produced having outstanding resistance to oils and heat by a rigid polyvinyl chloride resin reinforcement embedded in the rubber layer forming a firm bond between said reinforcement and the rubber layer uniformly over the entire periphery and effectively preventing separation therebetween when the hose is subjected to repeated bending and deformation over a prolonged period of time.
 7. The invention of claim 1 wherein at least two of said plurality of feed rollers are rotatable in the same direction and inclined in the same direction with respect to the axis of the tubular body being produced.
 8. The invention of claim 1 wherein said plurality of feed rollers are rotatable in the same direction and arranged on the same circumference in parallel to one another, and outer rollers having cam surfaces disposed close to a group of said rollers or cam surfaces arranged at base ends of the rollers successively displaced in the axial direction.
 9. The invention of claim 8 wherein said strip is helically wound over said group of said rollers and is forced toward the free end by the roller cam surfaces or by the cam surfaces.
 10. The invention of claim 1 wherein a plurality of rotatable shafts are arranged around a tubular rotary shaft or on the same circumference, and a belt helically wound around the group of rotatable shafts, the belt having opposite ends connected together in the hollow portion of the tubular rotary shaft or in a hollow portion defined by the group of the rotatable shafts to provide an endless helical rotatable member forming said strip, when helically wound on the rotatable member said tubular body being sent toward the free end.
 11. The invention of claim 1 wherein a plurality of rotatable shafts are arranged on a same circumference in parallel to one another, and sleeves covering the shafts are respectively and reciprocally slidable only axially thereof.
 12. The invention of claim 1 wherein said strip is helically wound around the group of sleeves into a tubular body, each of the sleeves comprising two divided semicylindrical segments being slidable toward the free end when brought into contact with the inner surface of the tubular body, the segments being also slidable in the reverse direction when brought away from the inner surface of the body.
 13. The invention of claim 1 wherein said heating means has the nichrome wire heater provided on the outer peripheral surface of the metal core, said metal core formed with an oil passage through which a high-temperature oil heated outside the former is circulated.
 14. The invention of claim 1 wherein said reinforcement of rigid polyvinyl chloride resin and metal wire is embedded in a soft resin layer and a rubber layer being vulcanized from inside by the heating means in the former.
 15. The invention of claim 1 wherein said tube is in the form of a rubber layer and a rigid resin reinforcement is provided helically around the tubular portion forming a hose produced by continuously extruding from the extruder a strip composed of an unvulcanized rubber portion and a reinforcement intimately fused and bonded to the top center part of the rubber portion, helically winding the strip on the former into a tubular body with one side edge of the unvulcanized rubber portion overlapping the other side edge thereof, and heating and vulcanizing the tubular body from inside by the heating means in the former.
 16. The invention of claim 1 wherein said tube is comprised of inner and outer resin layers, a foamed resin layer 25 having a reinforcement embedded therein, the tube being made by helically winding on the former said strip for forming the layers into a tubular body, and heating the tubular body from inside by the heating means within the former B to foam the layer.
 17. The invention of claim 1 wherein when a hose is formed from said resin strip having higher heat resistance in its inner layer than in the outer layer thereof, the strip is heat-treated from inside, whereby one edge of the strip can be fused and bonded to the other edge effectively. 